Method for controlling transmission power, and apparatus for same

ABSTRACT

A method for controlling transmission powers by a communication apparatus in a wireless communication system supporting a plurality of component carriers. When a sounding reference symbol (SRS) transmission overlaps with a physical uplink shared channel (PUSCH) transmission in a time domain, the communication apparatus checks whether a total of a PUSCH transmission power for the PUSCH transmission on a first component carrier and a SRS transmission power for the SRS transmission on a second component carrier exceeds a maximum transmission power configured for the communication apparatus, and drops the SRS transmission if the total of the PUSCH transmission power and the SRS transmission power exceeds the maximum transmission power configured for the communication apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/231,335, filed on Aug. 8, 2016, which is a Continuation of U.S.application Ser. No. 14/949,093, filed on Nov. 23, 2015 (now U.S. Pat.No. 9,456,424 issued on Sep. 27, 2016), which is a Continuation of U.S.application Ser. No. 14/694,718, filed on Apr. 23, 2015 (now U.S. Pat.No. 9,215,672 issued on Dec. 15, 2015), which is a Continuation of U.S.application Ser. No. 14/327,313, filed on Jul. 9, 2014 (now U.S. Pat.No. 9,042,219 issued on May 26, 2015), which is a Continuation of U.S.application Ser. No. 13/145,515, filed on Jul. 20, 2011 (now U.S. Pat.No. 8,811,249 issued on Aug. 19, 2014), which was filed as the NationalPhase of PCT/KR2010/000511, filed on Jan. 28, 2010, which claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Application Nos.61/286,380, filed on Dec. 15, 2009, 61/255,868, filed on Oct. 29, 2009,61/246,489, filed on Sep. 28, 2009, 61/229,280, filed on Jul. 29, 2009,and 61/148,368, filed on Jan. 29, 2009, and under 35 U.S.C. §119(a) toPatent Application No. 10-2010-0007529 filed in the Republic of Korea onJan. 27, 2010. The contents of all of these applications are herebyincorporated by reference as fully set forth herein in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless communication system, andmore particularly, to a method and device for controlling an uplinktransmission power.

Wireless communication systems have been widely deployed to provide avariety of types of communication services such as voice or data.Generally, wireless communication systems are multiple access systemscapable of supporting communication with multiple users by sharingavailable system resources (bandwidth, transmission power, etc.).Examples of the multiple access system include a Code Division MultipleAccess

(CDMA) system, a Frequency Division Multiple Access (FDMA) system, aTime Division Multiple Access (TDMA) system, an Orthogonal FrequencyDivision Multiple Access (OFDMA) system, a Single Carrier FrequencyDivision Multiple Access (SC-FDMA) system, a Multi Carrier FrequencyDivision Multiple Access (MC-FDMA) system, and the like.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method and device forefficiently controlling a transmission power when transmitting aplurality of signals in a wireless communication system.

Another object of the present invention is to provide a method anddevice for efficiently controlling a transmission power when the sum oftransmission powers of signals exceeds a maximum transmission power whentransmitting a plurality of signals in a wireless communication system.

Technical problems to be solved by the present invention are not limitedto the above-mentioned technical problem, and other technical problemsnot mentioned above can be clearly understood by one skilled in the artfrom the following description.

In one aspect of the present invention, a method for transmittingsignals in a wireless communication system includes independentlydetermining transmission powers of a first channel and a second channel,reducing at least one of the transmission powers of the first and secondchannels in consideration of channel priority if the sum of thetransmission powers of the first and second channels exceeds a maximumtransmission power, and simultaneously transmitting signals to a basestation through the first and second channels.

In another aspect of the present invention, a User Equipment (UE)includes a Radio Frequency (RF) unit for transmitting and receiving aradio signal to and from a Base Station (BS), a memory for storinginformation transmitted and received to and from the BS and parametersnecessary for operation of the UE, and a processor connected to the RFunit and the memory and configured to control the RF unit and the memoryfor operation of the UE, wherein the processor independently determinestransmission powers of a first channel and a second channel, reduces atleast one of the transmission powers of the first and second channels inconsideration of channel priority if the sum of the transmission powersof the first and second channels exceeds a maximum transmission power,and simultaneously transmits signals to a base station through the firstand second channels.

Each of the first and second channels may include one or more SingleCarrier Frequency Division Multiple Access (SC-FDMA) symbols. Meanwhile,the channel priority may be determined considering at least one of achannel type or information on a channel. Each of the channels mayinclude any one of a Physical Uplink Shared CHannel (PUSCH), a PhysicalUplink Control CHannel (PUCCH), or a Sounding Reference Signal (SRS).

If both the first channel and the second channel are PUSCHs, the channelpriority may be determined considering at least one of a transmissionformat, retransmission/non-retransmission, or the number ofretransmissions. If a transmission power of a PUSCH is reduced, aModulation and Coding Scheme (MCS) applied to the PUSCH may becontrolled as a low value in consideration of a reduced power amount. Ifthe first channel is a PUCCH transmitting an ACK and the second channelis a PUSCH, high channel priority may be allocated to the PUSCH.

In a further aspect of the present invention, a method for transmittingsignals at a User Equipment (UE) in a wireless communication systemincludes confirming a maximum transmission power (P_CC_MAX) percomponent carrier of a plurality of component carriers and a maximumtransmission power (P_UE_MAX) of the UE, calculating respectivetransmission powers for a plurality of channels scheduled to besimultaneously transmitted to a Base Station (BS) through one or morecomponent carriers, independently adjusting the transmission powers forthe plurality of channels so as not to exceed the P_CC_MAX and theP_UE_MAX, and transmitting signals to the BS through the plurality ofchannels for which the transmission powers are adjusted.

In another aspect of the present invention, a User Equipment (UE)includes a Radio Frequency (RF) unit for transmitting and receiving aradio signal to and from a Base Station (BS), a memory for storinginformation transmitted and received to and from the BS and parametersnecessary for operation of the UE, and a processor connected to the RFunit and the memory and configured to control the RF unit and the memoryfor operation of the UE, wherein the processor confirms a maximumtransmission power (P_CC_MAX) per component carrier of a plurality ofcomponent carriers and a maximum transmission power (P_UE_MAX) of theUE, calculates respective transmission powers for a plurality ofchannels scheduled to be simultaneously transmitted to a Base Station(BS) through one or more component carriers; independently adjusts thetransmission powers for the plurality of channels so as not to exceedthe P_CC_MAX and the P_UE_MAX, and transmits signals to the BS throughthe plurality of channels for which the transmission powers areadjusted.

Information for setting the P_CC_MAX and information for setting theP_UE_MAX may be signaled through a broadcast message or a Radio ResourceControl (RRC) message.

The adjustment of the transmission powers for the plurality of channelsmay include independently reducing transmission powers of the respectivechannels so that the sum of the transmission powers of the plurality ofchannels does not exceed the P_UE_MAX, and, after the reducingtransmission powers of the respective channels, independently reducingtransmission powers of corresponding channels per component carrier sothat the sum of the transmission powers of the corresponding channelsdoes not exceed a corresponding P_CC_MAX. In this case, at least a partof the reduced powers from the corresponding channels may be used toincrease transmission powers of other component carriers.

The adjustment of the transmission powers for the plurality of channelsmay include independently reducing transmission powers of correspondingchannels per component carrier so that the sum of the transmissionpowers of the corresponding channels does not exceed a correspondingP_CC_MAX, and, after the reducing transmission powers of the respectivechannels, independently reducing transmission powers of the respectivechannels so that the sum of the transmission powers of the plurality ofchannels does not exceed the P_UE_MAX.

The adjustment of the transmission powers for the plurality of channelsmay include independently applying an attenuation coefficient to therespective channel.

Each of the channels may include one or more Single Carrier FrequencyDivision Multiple Access (SC-FDMA) symbols. In this case, each of thechannels may include any one of a Physical Uplink Shared CHannel(PUSCH), a Physical Uplink Control CHannel (PUCCH), or a SoundingReference Signal (SRS).

In another aspect of the present invention, a method for transmittingsignals at a User Equipment (UE) in a wireless communication systemincludes calculating a transmission power of each of a plurality ofantennas, calculating transmission power attenuation ratios if thecalculated transmission power exceeds a maximum transmission power of acorresponding antenna, identically applying a maximum attenuation ratioamong the transmission power attenuation ratios to the plurality ofantennas, and transmitting a signal to a Base Station (BS) through theplurality of antennas.

According to exemplary embodiments of the present invention, atransmission power can be efficiently controlled when transmitting aplurality of signals in a wireless communication system. Furthermore, atransmission power can be efficiently controlled when the sum oftransmission powers of signals exceeds a maximum transmission power.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a network structure of an Evolved Universal MobileTelecommunications System (E-UMTS);

FIG. 2, including view (a) and view (b), illustrates the structure of aradio interface protocol between a UE and an E-UTRAN based on the 3GPPradio access network standard;

FIG. 3 illustrates a block diagram of a transmitter and a receiver forOFDMA and SC-FDMA;

FIG. 4 illustrates the structure of a radio frame used in an LTE system;

FIG. 5 illustrates an example of performing communication in a singlecomponent carrier environment;

FIG. 6A illustrates the structure of a UL subframe used in an LTEsystem;

FIG. 6B illustrates the structure of a UL control channel used in an LTEsystem;

FIG. 7 illustrates an example of performing communication in a multiplecomponent carrier environment;

FIG. 8 illustrates exemplary transmission power control according to anembodiment of the present invention;

FIG. 9 illustrates an example of transmitting a plurality of signalsaccording an embodiment of the present invention;

FIG. 10, including views (a), (b) and (c), illustrates an example ofcontrolling a transmission power according to an embodiment of thepresent invention when a maximum transmission power is limited in unitsof one or more component carriers;

FIG. 11, including views (a), (b), (c) and (d), illustrates anotherexample of controlling a transmission power according to an embodimentof the present invention when a maximum transmission power is limited inunits of one or more component carriers; and

FIG. 12 illustrates a base station and a user equipment that areapplicable to the embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The configuration, operation, and other characteristics of the presentinvention may be understood by the embodiments of the present inventiondescribed with reference to the accompanying drawings. Herein, theembodiments of the present invention may be used in various wirelessaccess technologies, such as CDMA, FDMA, TDMA, OFDMA, SC-FDMA, andMC-FDMA. CDMA may be implemented with wireless technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may beimplemented with wireless technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA may be implemented with wirelesstechnology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, and E-UTRA (Evolved UTRA). UTRA is part of a Universal MobileTelecommunications System (UMTS). 3rd Generation Partnership Project(3GPP) Long Term Evolution (LTE) is a part of an Evolved UMTS (E-UMTS),which uses E-UTRA. LTE-A (Advanced) is an evolved version of 3GPP LTE.

The following embodiments of the present invention mainly describeexamples of the technical characteristics of the present invention asapplied to the 3GPP system. However, this is merely exemplary.Therefore, the present invention will not be limited to the embodimentsof the present invention described herein.

FIG. 1 illustrates a network structure of an E-UMTS. The E-UMTS is alsocalled an LTE system. For details of the technical specifications of theUMTS and E-UMTS, refer to Release 7 and Release 8 of “3rd GenerationPartnership Project; Technical Specification Group Radio AccessNetwork”, respectively.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE) 120,eNode Bs (or eNBs) 110 a and 110 b, and an Access Gateway (AG) which islocated at an end of a network (E-UTRAN) and is connected to an externalnetwork. The eNode Bs may simultaneously transmit multiple data streamsfor a broadcast service, a multicast service, and/or a unicast service.One or more cells may exist per eNode B. A cell is set to use one ofbandwidths of 1.25, 2.5, 5, 10, and 20 MHz. Different cells may be setto provide different bandwidths. The eNode B controls data transmissionand reception for a plurality of UEs. The eNode B transmits downlink(DL) scheduling information with respect to DL data to notify acorresponding UE of a time/frequency domain in which data is to betransmitted, coding, data size, and Hybrid Automatic Repeat and reQuest(HARQ)-related information. In addition, the eNode B transmits uplink(UL) scheduling information with respect to UL data to inform acorresponding UE of an available time/frequency domain, coding, datasize, and HARQ-related information. A Core Network (CN) may include theAG, a network node for user registration of the UE, and the like. The AGmanages mobility of a UE on a Tracking Area (TA) basis, wherein one TAincludes a plurality of cells.

FIG. 2, including view (a) and view (b), illustrates the structures of acontrol plane and a user plane of a radio interface protocol between aUE and an E-UTRAN based on the 3GPP radio access network standard. Asshown in FIG. 2(a), the control plane refers to a path used fortransmitting control messages which are used in the UE and the networkto manage a call. As shown in FIG. 2(b), the user plane refers to a pathused for transmitting data generated in an application layer, e.g.,voice data or Internet packet data.

A physical (PHY) layer, which is a first layer, provides an informationtransfer service to an upper layer using a physical channel. The PHYlayer is connected to a Medium Access Control (MAC) layer of an upperlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is also transportedbetween a physical layer of a transmitting side and a physical layer ofa receiving side via a physical channel. The physical channel uses timeand frequency as radio resources. Specifically, the physical channel ismodulated using an OFDMA scheme in DL and is modulated using an SC-FDMAscheme in UL.

A MAC layer of a second layer provides a service to a Radio Link Control(RLC) layer of an upper layer via a logical channel. The RLC layer ofthe second layer supports reliable data transmission. The function ofthe RLC layer may be implemented by a functional block within the MAC. APacket Data Convergence Protocol (PDCP) layer of the second layerperforms a header compression function to reduce unnecessary controlinformation for efficient transmission of an Internet Protocol (IP)packet such as IPv4 or IPv6 in a radio interface having a narrowbandwidth.

A Radio Resource Control (RRC) layer located at the bottommost portionof a third layer is defined only in the control plane. The RRC layercontrols logical channels, transport channels, and physical channels inrelation to configuration, re-configuration, and release of RadioBearers (RBs). The RB refers to a service provided by the second layerto transmit data between the UE and the network. To this end, the RRClayer of the UE and the RRC layer of the network exchange RRC messages.The UE is in an RRC connected mode if an RRC connection has beenestablished between the RRC layer of the radio network and the RRC layerof the UE. Otherwise, the UE is in an RRC idle mode. A Non-AccessStratum (NAS) layer located at an upper level of the RRC layer performsfunctions such as session management and mobility management.

DL transport channels for data transmission from the network to the UEinclude a Broadcast Channel (BCH) for transmitting system information, aPaging Channel (PCH) for transmitting paging messages, and a DL SharedChannel (DL-SCH) for transmitting user traffic or control messages.Meanwhile, UL transport channels for data transmission from the UE tothe network include a Random Access Channel (RACH) for transmittinginitial control messages and a UL Shared Channel (UL-SCH) fortransmitting user traffic or control messages.

FIG. 3 illustrates a block diagram of a transmitter and a receiver forOFDMA and SC-FDMA. In UL, a transmitter (402-414) is a part of a UE anda receiver (416-430) is a part of an eNode B. In DL, the transmitter isa part of the eNode B and the receiver is a part of the UE.

Referring to FIG. 3, an OFDMA transmitter includes a serial-to-parallelconverter 402, a subcarrier mapping module 406, an M-point InverseDiscrete Fourier Transform (IDFT) module 408, a Cyclic Prefix (CP)adding module 410, a parallel-to-serial converter 412, and a RadioFrequency (RF)/Digital-to-Analog Converter (DAC) module 414.

Signal processing in the OFDMA transmitter proceeds as follows. First, abitstream is modulated into a data symbol sequence. The bitstream may beobtained by performing various types of signal processing includingchannel encoding, interleaving, scrambling, etc. on a data blockdelivered from a MAC layer. The bitstream is also referred to as acodeword and is equivalent to a data block received from the MAC layer.The data block received from the MAC layer is referred to as a transportblock as well. A modulation scheme may include, without being limitedto, Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying(QPSK), and n-Quadrature Amplitude Modulation (n-QAM). Next, a serialdata symbol sequence is converted into N data symbols in parallel (402).The N data symbols are mapped to N subcarriers allocated among a totalof M subcarriers and the (M−N) remaining subcarriers are padded with Os(406). The data symbol mapped in a frequency domain is converted to atime-domain sequence through M-point IFFT processing (408). Thereafter,in order to reduce Inter-Symbol Interference (ISI) and Inter-CarrierInterference (ICI), an OFDMA symbol is generated by adding a CP to thetime-domain sequence (410). The generated parallel OFDMA symbol isconverted into serial OFDMA symbol (412). The OFDMA symbol is thentransmitted to a receiver through digital-to-analog conversion,frequency upconversion, and the like (414). Available subcarriers amongthe (M−N) remaining subcarriers are allocated to another user.Meanwhile, an OFDMA receiver includes an RF/Analog-to-Digital Converter(ADC) module 416, a serial-to-parallel converter 418, a CP removingmodule 420, an M-point Discrete Fourier Transform (DFT) module 422, asubcarrier demapping/equalization module 424, a parallel-to-serialconverter 428, and a detection module 430. A signal processing processof the OFDMA receiver has a configuration reverse to that of the OFDMAtransmitter.

Meanwhile, compared to the OFDMA transmitter, an SC-FDMA transmitterfurther includes an N-point DFT module 404 located before the subcarriermapping module 406. The SC-FDMA transmitter spreads a plurality of datain a frequency domain through DFT prior to IDFT processing, therebyconsiderably decreasing a Peak-to-Average Power Ratio (PAPR) of atransmission signal in comparison with an OFDMA scheme. Compared to theOFDMA receiver, an SC-FDMA receiver further includes an N-point IDFTmodule 426 after the subcarrier demapping module 424. A signalprocessing process of the SC-FDMA receiver has a configuration reverseto that of the SC-FDMA transmitter.

FIG. 4 illustrates the structure of a radio frame used in an LTE system.

Referring to FIG. 4, a radio frame has a length of 10 ms (327200 T_(s))and includes 10 equally sized subframes. Each of the subframes has alength of 1 ms and includes two slots. Each of the slots has a length of0.5 ms (15360 T_(s)). In this case, T_(s) denotes a sampling time, andis represented by T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns). Eachslot includes a plurality of OFDM symbols in a time domain and includesa plurality of Resource Blocks (RBs) in a frequency domain. In the LTEsystem, one RB includes 12 subcarriers×7 (or 6) OFDM symbols. ATransmission Time Interval (TTI) which is a unit time for datatransmission may be determined in units of one or more subframes. Theabove-described radio frame structure is purely exemplary and variousmodifications may be made in the number of subframes, the number ofslots or the number of OFDM symbols, included in the radio frame.

FIG. 5 illustrates an example of performing communication in a singlecomponent carrier environment. FIG. 5 may correspond to an example ofcommunication in an LTE system.

Referring to FIG. 5, in an FDD scheme, communication is generallyperformed through one DL band and through one UL band corresponding tothe DL band. In a TDD scheme, communication is performed through a DLduration and through a UL duration corresponding to the DL duration. Inthe FDD or TDD scheme, data and/or control information may betransmitted and received in units of subframes. A UE reducesinterference with neighboring cells caused by an excessive transmissionpower and optimizes the amount of used power through a power controlscheme, by raising a power in a bad channel environment and lowering apower in a good channel environment during transmission. In the casewhere a channel environment is not good, a Base Station (BS) commandsthat the power of a UE be raised. However, a command indicating that thepower of the UE exceeds a maximum transmission power (i.e. transmissionpower limitation P^(UE) _(Max) or P_(Max)) of the UE is disregarded.

FIG. 6A illustrates the structure of a UL subframe used in an LTEsystem.

Referring to FIG. 6A, an UL subframe includes a plurality of slots (e.g.two slots). A slot may include a different number of SC-FDMA symbolsaccording to the length of a CP. For example, in a normal CP, a slotincludes 7 SC-FDMA symbols. The UL subframe is divided into a dataregion and a control region. The data region includes a Physical UplinkShared CHannel (PUSCH) and is used to transmit data signals such asvoice and images. The power of a data signal is determined based on thepower of a Reference Signal (RS) included in the same region. Forexample, the power of the data signal may be determined based on thepower of a DeModulation Reference Signal (DMRS).

The control region includes a Physical Uplink Control CHannel (PUCCH)and transmits various control information to UL. The PUCCH includes aResource Block (RB) pair located at both ends of the data region in afrequency domain and hops based on a slot. A transmission power ofcontrol information is determined based on a transmission power of acontrol channel reference signal located in the PUCCH. Details of thestructure of the PUCCH will be described later with reference to FIG.6B. A Sounding Reference Signal (SRS) for UL channel measurement islocated in the last SC-FDMA symbol of a subframe and is transmittedthrough all or some bands of the data region.

UL transmission in the LTE system exhibits single carrier characteristicusing SC-FDMA and the PUSCH, PUCCH, and SRS are not permitted to besimultaneously transmitted. SC-FDMA enables a power amplifier to beefficiently used by maintaining a low PAPR compared to a multi-carriersystem (e.g. OFDM). Accordingly, if both data and control signals shouldbe simultaneously transmitted, information which should be transmittedthrough the PUCCH is multiplexed with data in a piggyback manner.Moreover, in an SC-FDMA symbol in which the SRS is transmitted, thePUSCH or the PUCCH is not transmitted. Power control of the PUSCH isindependent of power control of the PUCCH.

FIG. 6B illustrates the structure of a PUCCH used in an LTE system.

Referring to FIG. 6B, in a normal CP, UL RSs are conveyed in threesuccessive symbols located in the middle of a slot and controlinformation (i.e. ACK/NACK) is conveyed in the four remaining symbols.In an extended CP, a slot includes 6 symbols and RSs are conveyed in thethird and fourth symbols. The control information further includes aChannel Quality Indicator (CQI), a Scheduling Request (SR), a PrecodingMatrix Index (PMI), a Rank Indicator (RI), and the like. A transmissionpower of the control information is determined based on a transmissionpower of a UL RS. In the structure of the PUCCH, the number and positionof UL RSs vary according to types of the control information. Resourcesfor the control information are distinguished using different CyclicShifts (CSs) (frequency spread) and/or different Walsh/DFT orthogonalcodes (time spread) of a Computer Generated Constant Amplitude Zero AutoCorrelation (CG-CAZAC) sequence. Even if w0, w1, w2, and w3 multipliedafter IFFT are multiplied before the IFFT, the same result is obtained.An Orthogonal Cover (OC) sequence of a corresponding length may bemultiplied to the RS.

FIG. 7 illustrates an example of performing communication in a multiplecomponent carrier environment. Recently, a wireless communication system(e.g. an LTE-A system) uses carrier aggregation or bandwidth aggregationtechnology which uses a wider UL/DL bandwidth by aggregating a pluralityof UL/DL frequency blocks in order to employ a wider frequency band. Therespective frequency blocks are transmitted using a Component Carrier(CC). In this specification, the CC may refer to a frequency block forcarrier aggregation or a center carrier of the frequency block accordingto contexts and they are mixedly used.

Referring to FIG. 7, five 20 MHz CCs per each of UL/DL may support abandwidth of 100 MHz. The respective CCs may be adjacent to each otherin a frequency domain or may not be adjacent. For convenience, FIG. 7shows the case where a bandwidth of a UL CC is the same as a bandwidthof a DL CC and they are symmetrical. However, a bandwidth of each CC maybe independently determined. For example, a bandwidth of a UL CC may beconfigured as 5 MHz (A_(UL))+20 MHz (B_(UL))+20 MHz (C_(UL))+20 MHz(D_(UL))+5 MHz (E_(UL)). It is also possible to configure asymmetriccarrier aggregation in which the number of UL CCs is different from thenumber of DL CCs. Asymmetric carrier aggregation may be generated due tolimitation of available frequency bands or may be intentionallyperformed during network setup. For example, even if an entire systemband is comprised of N CCs, a frequency band which can be received by aspecific UE may be limited to M (<N) CCs. Various parameters for carrieraggregation may be set cell-specifically, UE group-specifically, orUE-specifically.

In the LTE-A system, a transmitting end may simultaneously transmit aplurality of signals/(physical) channels through a single CC or multipleCCs. For example, the same or different two or more channels selectedfrom the PUSCH, PUCCH, or SRS may be simultaneously transmitted.Accordingly, if a plurality of (physical) channels is transmittedwithout maintaining a single carrier transmission characteristic, it isnecessary to consider operation of a UE when a sum of transmissionpowers calculated with respect to the plurality of (physical) channelsreaches a maximum transmission power limitation. Unless otherwisementioned in this specification, a plurality of signals/(physical)channels refers to signals/(physical) channels, transmission powers ofwhich are independently determined. For example, a plurality ofsignals/(physical) channels includes signal/(physical) channelsassociated with different separate RSs. In this specification,transmission of a (physical) channel refers to transmission of a signalthrough a (physical) channel. In this specification, a signal and a(physical) channel are mixedly used.

Hereinafter, a method of controlling a transmission power will bedescribed in detail with reference to FIGS. 8 to 11. For convenience,although a description of FIGS. 8 to 11 is given in terms of a UE by wayof example, it may be easily applied by modification even when a BStransmits a plurality of signals. In the embodiments of the presentinvention, a transmission power may be expressed as a linear scale or adB scale. An operation according to the embodiments of the presentinvention may be carried out in a power domain or an amplitude domain.

Embodiment 1: Power Control Considering (Channel) Priority

FIG. 8 illustrates exemplary transmission power control according to anembodiment of the present invention. In this embodiment, it is proposedto control transmission powers of physical channels in consideration of(channel) priority when a sum of transmission powers of a plurality ofphysical channels exceeds a maximum transmission power.

Referring to FIG. 8, a UE may receive one or more Transmit Power Control(TPC) commands from a BS (S810). The TPC command may be included in aresponse message to a preamble for random access or may be transmittedthrough a Physical Downlink Control CHannel (PDCCH). The PDCCH may havevarious formats according to Downlink Control Information (DCI) and mayhave different TPC commands according to formats. For example, a UE mayreceive a PDCCH of various formats, such as a format for DL scheduling,a format for UL scheduling, a TPC dedicated format for a PUSCH, and aTPC dedicated format for a PUCCH. The TPC command may be used todetermine a transmission power for each CC, a transmission power for aCC group, or a transmission power for all CCs. The TPC command may alsobe used to determine a transmission power for each signal (e.g. a PUSCH,a PUCCH, etc.). The TPC command may be received through a PDCCH ofvarious formats, such as a format for DL scheduling, a format for ULscheduling, a TPC dedicated format for a UL data channel (e.g. a PUSCH),and a TPC dedicated format for a UL control channel (e.g. a PUCCH).

If there is a plurality of physical channels scheduled to besimultaneously transmitted to the BS, the UE individually determinestransmission powers P₁, P₂, . . . , P_(N) (where N≧2) for a plurality ofUL physical channels (S820). Each of the UL physical channels includesone or more successive OFDMA symbols or SC-FDMA symbols. An example ofthe case where the UE transmits a plurality of signals to UL isillustrated in, but not limited to, FIG. 9. Referring to FIG. 9, aplurality of physical channels may be simultaneously transmitted using asingle CC or multiple CCs. For example, a plurality of PUCCHs, aplurality of PUSCHs, or a plurality of SRSs may be simultaneouslytransmitted (Cases 1 to 3) or combinations of a PUCCH, a PUSCH, and/oran SRS may be simultaneously transmitted (Cases 4 to 7). In the case ofthe PUCCH, detailed classification into the cases of transmitting anACK/NACK, a CQI, and an SR is possible.

If the UL transmission powers are determined, the UE checks whether asum total ΣP_(n) (where 1≦n≦N) of the transmission powers of the ULphysical channels is greater than a maximum power value P_(Max) (S830).The maximum power value may be determined in units of a CC, a CC group,or total CCs. The maximum power value depends basically on physicalability of the UE but may be previously determined according to acommunication system. The maximum power value may be changed inconsideration of a permissible power within a cell, load balancing, etc.Accordingly, in this specification, the maximum power value may bemixedly used with a maximum permissible power value and the two may beused interchangeably. Information about the maximum power value may bebroadcast through a broadcast message (e.g. system information) within acell or may be signaled through an RRC message. The information aboutthe maximum power value may be transmitted to the UE through a DLcontrol channel (e.g. a PDCCH). The maximum power value may be setpermanently, semi-permanently, or dynamically according to channelenvironments. When the maximum power value is limited by signaling ofthe BS, it may have the same meaning as the maximum permissible powerwithin a cell. For example, the maximum power value may be previouslydetermined, or may be designated cell-specifically, UEgroup-specifically, UE-specifically, CC group-specifically, orCC-specifically.

If the sum total ΣP_(n) (where 1≦n≦N) of the transmission powers of theUL physical channels is equal to or less than the maximum power valueP_(Max), transmission powers of corresponding UL physical channels aremaintained. Meanwhile, if the sum total of the UL transmission powers ofUL physical channels is greater than the maximum power value,transmission powers of one or more UL physical channels are controlledso that the sum total of the transmission powers of the UL physicalchannels does not exceed the maximum power value in consideration ofpriority (S840). Priority may be determined considering types of the ULphysical channels and information carried on the UL physical channels.Priority will be described in detail later. The transmission powers maybe controlled with respect to all bands or in units of CC groups or CCs.

If the transmission powers of the UL physical channels are controlled,the UE generates a plurality of UL physical channels havingcorresponding transmission powers (S850). The transmission powers of theUL physical channels may be controlled in a frequency domain prior tothe IFFT (408 of FIG. 3). However, the present invention is not limitedthereto. In this case, control of the transmission powers may beperformed in units of subcarriers. For example, the transmission powersmay be controlled by multiplying a weight by a modulation value mappedto subcarriers. The weight may be multiplied using a diagonal matrix (apower diagonal matrix) in which each element indicates a value relatedto a transmission power. In the case of a Multiple Input Multiple Output(MIMO) system, a transmission power may be controlled using a precodingmatrix in which a weight is incorporated or may be controlled bymultiplying a power diagonal matrix by a precoded modulation value.Accordingly, even if a plurality of physical channels is included withina frequency band to which the same IFFT is applied, a transmission powerof each physical channel can be easily controlled. Together with orseparately from power control in a frequency domain, transmission powersof UL physical channels may be controlled in a time domain after IFFT.Specifically, the control of transmission powers in a time domain may beperformed in various functional blocks. For example, the control oftransmission powers may be performed in the DAC block and/or the RFblock (414 of FIG. 3). Thereafter, the UE transmits a plurality ofgenerated UL physical channels to the BS through one or more CCs (S860).In this specification, a simultaneous or same time duration includes thesame TTI or subframe.

A method for controlling transmission powers of UL channels inconsideration of priority in step S840 of FIG. 8 is described in detail.For convenience, an exemplary power control method according to an equalorder or priority is described when only two channels are present.However, the present invention is applicable to three or more same ordifferent types of channels or to combinations thereof.

For convenience of description, the following symbols are defined.

P_(PUSCH): this indicates a power calculated to be allocated to a PUSCH.An actually allocated power may be less than P_(PUSCH) by powerlimitation. If there is no indication of dB, this may mean a linearscale.

P_(PUCCH): this indicates a power calculated to be allocated to a PUCCH.An actually allocated power may be less than P_(PUCCH) by powerlimitation. If there is no indication of dB, this may mean a linearscale.

P_(SRS): this indicates a power calculated to be allocated to an SRS. Anactually allocated power may be less than P_(SRS) by power limitation.If there is no indication of dB, this may mean a linear scale.

P _(PUSCH) +P _(PUSCH) >P _(Max)  Case 1-1:

Case 1-1 corresponds to the case where a plurality of PUSCHssimultaneously transmitted in a plurality of different CCs reaches amaximum transmission limitation. In this case, it is possible to reduceor drop a transmission power of each PUSCH. Specifically, the followingoptions may be considered.

Option 1: PUSCHs may be given the same priority. If so, it may bepossible to reduce powers of the PUSCHs at the same rate or reduce thesame amount of the powers of the PUSCHs. That is, the same attenuationrate may be applied or the same value is subtracted.

Option 2: PUSCHs may be given priority in consideration of transportformats of the PUSCHs. For example, priority may be determined accordingto a Transport Block Size (TBS) or a Modulation and Coding Scheme (MCS)to sequentially reduce or drop a transmission power of a PUSCH havinglow priority. Desirably, a PUSCH having a small TBS (data amount), a lowMCS (a low code rate), or a low modulation order is given low priority.In this case, a higher attenuation rate may be applied to a PUSCH havinglow priority. However, if a transmission power exceeds the maximumtransmission limitation even though only one PUSCH remains due to dropof a PUSCH, a power of a corresponding PUSCH is reduced to P_(Max)during transmission.

P _(PUCCH(ACK/NACK)) +P _(PUSCH) >P _(Max)  Case 1-2:

Case 1-2 is when the sum of transmission powers of a PUCCH transmittingan ACK/NACK and a PUSCH reaches a maximum power limitation in differentCCs or in one CC. The following options may be considered.

Option 1: An ACK/NACK may be given priority. A UL ACK/NACK serves toreport success or failure of DL data reception. If such report is notproperly made, DL resources are wasted. Accordingly, high priority isallocated to transmission of the ACK/NACK and a transmission power of aPUSCH is reduced or dropped during transmission. In case of reducing thetransmission power of the PUSCH, a transmission power may be firstallocated to the PUCCH and the remaining power may be allocated to thePUSCH. This can be expressed by the following equation:P_(PUSCH)=P_(max)−P_(PUCCH(ACK/NACK)). Here, the following option may beadditionally applied.

Option 1.1: Since a power remaining after a transmission power isallocated to the PUCCH is used for the PUSCH, an error rate of the PUSCHincreases. Therefore, an MCS of data transmitted to the PUSCH is reducedduring transmission so that the PUSCH can be received at the same errorrate as an error rate before a power reduction. To this end, informationabout the reduced MCS may be signaled to the BS.

Option 2: The PUSCH may be given priority. If a power of the PUCCHtransmitting the ACK/NACK is reduced, DL resources are wasted due to areception error of the UL ACK/NACK. Especially, if a NACK is recognizedas an ACK, retransmission of an upper layer occurs and transmission ofDL data is more delayed. Meanwhile, if an ACK is recognized as a NACK,only a waste of retransmission in a physical layer occurs. Accordingly,in the case of transmitting urgent data, it may be considered to firstallocate a power to the PUSCH and to allocate the remaining power(decreased power) to the PUCCH, in preparation for the case where datais delayed due to transmission of the PUSCH at a continuous low power.In this case, it is desirable that the power decrease of the PUCCH belimited to the case where the PUCCH transmits the ACK.

P _(SRS) +P _(PUSCH) >P _(Max)  Case 1-3:

Case 1-3 corresponds to the case where the sum of transmission powers ofan SRS and a PUSCH reaches a maximum power limitation in different CCsor one CC. The following options may be considered.

Option 1: SRS transmission may be given priority. An SRS is used when aBS performs optimal UL scheduling by measuring a UL channel state. Highpriority may be allocated to the SRS in consideration of the efficiencyof next scheduling. Then a transmission power of the PUSCH is reduced ordropped during transmission. To reduce the transmission power of thePUSCH, a transmission power may be first allocated to the SRS and theremaining power may be allocated to the PUSCH. This may be expressed as:P_(PUSCH)=P_(Max)−P_(SRS). In this case, the following option may beadditionally applied.

Option 1.1: Since a power remaining after a transmission power isallocated to the SRS is used for the PUSCH, an error rate of the PUSCHincreases. Therefore, an MCS of data transmitted to the PUSCH is reducedduring transmission so that the PUSCH can be received at the same errorrate as an error rate before power reduction. To this end, informationabout the reduced MCS may be signaled to the BS.

Option 2: PUSCH transmission may be given priority. If the transmissionpower of the SRS is reduced, channel information may be misjudgedbecause a BS is not aware of whether a reduction of a received power isdue to a bad environment state of a UL radio channel or due totransmission of a power decreased by a UE. Accordingly, if atransmission power is insufficient, an SRS may be dropped.

P _(PUCCH(ACK/NACK)) +P _(PUCCH(ACK/NACK)) >P _(Max)  Case 1-4:

Case 1-4 corresponds to the case where the sum of transmission powers ofa plurality of PUCCHs transmitting ACKs/NACKs reaches a maximum powerlimitation. In this case, a transmission power of each PUCCH is reducedor dropped. Specifically, the following options may be considered.

Option 1: PUCCHs transmitting the ACK/NACK may be given the samepriority. If so, it may be possible to reduce powers of the PUSCHs atthe same rate or reduce the same amount of the powers of the PUSCHs.That is, the same attenuation rate may be applied or the same value issubtracted.

Option 2: Powers of a part of the PUCCHs may be reduced or droppedaccording to priority.

Option 2.1: If a NACK is recognized as an ACK, resource waste andtransmission delay is more severe than in the case where the ACK isrecognized as the NACK. Accordingly, a transmission power of a PUCCHtransmitting the ACK is first reduced or dropped. It can be consideredto set a specific threshold and to reduce the power up to the threshold.

Option 2.2: Priority of the PUCCHs is determined according to a TBS oran MCS of a PDSCH corresponding to an ACK/NACK of each PUCCH and atransmission power of a PUCCH having low priority is reduced or dropped.It is desirable to allocate low priority to a PDSCH of a small TBS or alow MCS. However, in the case of dropping a PUCCH, if a transmissionpower exceeds the maximum power limitation even though only one PUCCHremains, a power of a corresponding PUCCH is reduced to P_(max) duringtransmission.

P _(PUCCH(CQI)) +P _(PUCCH(CQI)) >P _(Max)  Case 1-5:

Case 1-5 corresponds to the case where the sum of transmission powers ofa plurality of PUCCHs transmitting CQIs in different CCs reaches amaximum power limitation. A CQI serves to perform efficient DLscheduling by recognizing the state of a DL radio channel. The followingoptions may be considered.

Option 1: PUCCHs transmitting the CQIs may be given the same priority.If so, it may be possible to reduce powers of the PUCCHs at the samerate or reduce the same amount of the powers of the PUCCHs. That is, thesame attenuation rate may be applied or the same value is subtracted.

Option 2: Powers of a part of the PUCCHs may be reduced or droppedaccording to priority. A BS performs scheduling for a UE by selecting aradio channel having a high CQI. Since a channel having a low CQI isless likely to be selected by the BS, accurate reception is lessimportant. Accordingly, a transmission power of a PUCCH having a low CQIis first reduced or dropped during transmission. A specific thresholdmay be set and reduction of a power up to the threshold may beconsidered.

P _(PUCCH(ACK/NACK)) +P _(PUCCH(CQI)) >P _(Max)  Case 1-6:

Case 1-6 is applied when the sum of transmission powers of a pluralityof PUCCHs transmitting CQI(s) and ACK/NACK(s) reaches a maximum powerlimitation. As described earlier, an ACK/NACK is given high priority.Meanwhile, a CQI is used for effective DL scheduling as informationtransmitting the state of a DL channel to a BS. Even though a betterchannel is allocated to a UE, unnecessary retransmission occurs ifnormal reception of data is not accurately confirmed. Therefore, the CQIis given low priority. Namely, a power is first allocated to a PUCCHtransmitting the ACK/NACK, and a remaining power is allocated to a PUCCHtransmitting the CQI or the PUCCH transmitting the CQI is dropped.Meanwhile, a PUSCH transmitting both the CQI and the ACK/NACK is treatedin the same way as the PUCCH transmitting the ACK/NACK.

P _(PUCCH(SR)) +P _(PUCCH(ACK/NACK)) >P _(Max)  Case 1-7:

Case 1-7 corresponds to the case where the sum of transmission powers ofa plurality of PUCCHs transmitting SR(s) and ACK/NACK(s) reaches amaximum power limitation. The following options may be considered.

Option 1: ACK/NACK transmission may be given high priority. Accordingly,a power is first allocated to a PUCCH transmitting an ACK/NACK, and theremaining power is allocated to a PUCCH transmitting an SR or the PUCCHtransmitting the SR is dropped. Meanwhile, if the PUCCH transmitting theSR is dropped due to the continuous existence of the PUCCH transmittingthe ACK/NACK for a long time, UL scheduling is not possible. Tocompensate for this, if the PUCCH transmitting the SR is delayed for aspecific time, the PUCCH transmitting the ACK/NACK may be dropped.

Option 2: SR transmission may be given high priority. Since an error inACK/NACK transmission is solved by retransmission, high priority may beallocated to SR transmission by considering scheduling important and atransmission power of the PUCCH transmitting the ACK/NACK may be reducedor dropped during transmission. In the case of reducing the transmissionpower of the PUCCH transmitting the ACK/NACK, a transmission power maybe first allocated to the PUCCH transmitting the SR and the remainingpower may be allocated to the PUCCH transmitting the ACK/NACK. This canbe expressed as: P_(PUCCH(ACK/NACK))=P_(Max)−P_(SR).

Option 3: A UE transmits the ACK/NACK to the PUCCH transmitting the SR.Then, a BS may detect an on/off keyed SR in the PUCCH through energydetection and may judge the ACK/NACK through symbol decoding. In thiscase, if a plurality of PUCCHs transmitting the ACK/NACKs is present,ACK/NACK bundling or PUCCH selection transmission may be used. TheACK/NACK bundling indicates that one ACK is transmitted when all ACKsshould be transmitted by receiving a plurality of DL PDSCHs without anyerror and one NACK is transmitted when there is an error even in any oneof the DL PDSCHs. The PUCCH selection transmission represents aplurality of ACK/NACK results by transmitting a modulation value throughone PUCCH resource selected from a plurality of occupied PUCCH resourcesupon receiving a plurality of DL PDSCHs.

P _(PUSCH(UCI)) +P _(PUSCH) >P _(Max)  Case 1-8:

Case 1-8 corresponds to the case where the sum of transmission powers ofa PUSCH transmitting Uplink Control Information (UCI) and a PUCCHtransmitting data alone in different CCs reaches a maximum powerlimitation. The following options may be considered.

Option 1: The priority determination method described in Case 1-1 isused without considering the UCI. For example, PUSCHs may be given thesame priority. In this case, powers of the PUSCHs may be reduced at thesame rate. In consideration of transport formats of the PUSCHs,different priority may be allocated to the PUSCHs.

Option 2: Since control information is included in a PUSCH on which theUCI is piggybacked, high priority may be allocated to a channel on whichthe UCI is piggybacked. Accordingly, a transmission power of a PUSCHtransmitting data alone is reduced or dropped during transmission. Inthe case of reducing the transmission power of the PUSCH transmittingthe data alone, a transmission power is first allocated to the PUSCH onwhich the UCI is piggybacked and then the remaining power may beallocated to the PUSCH transmitting the data alone. This may beexpressed as: P_(PUSCH)=P_(Max)−P_(PUCCH(UCI)). In the case of reducingthe transmission power of the PUSCH transmitting the data alone, ahigher attenuation rate may be applied to the PUSCH transmitting thedata alone. However, if the transmission power exceeds the maximumtransmission power even though only one PUSCH remains due to drop of aPUCCH, a power of a corresponding PUSCH is reduced to P_(Max) duringtransmission.

P _(PUSCH(Retransmission)) +P _(PUSCH) >P _(Max)  Case 1-9:

Case 1-9 corresponds to the case where the sum of transmission powers ofa PUSCH transmitting retransmission data and a PUSCH transmitting newdata reaches a maximum power limitation.

Option 1: The priority determination method described in Case 1-1 isused without considering retransmission. For example, PUSCHs may begiven the same priority. In this case, powers of the PUSCHs may bereduced at the same rate. In consideration of transport formats of thePUSCHs, different priority may be allocated to the PUSCHs.

Option 2: Since retransmission may occur due to reduction of atransmission power during previous transmission, high priority may beallocated to a retransmitted PUSCH to improve a reception rate of thePUSCH.

P _(PUSCH(Retransmission)) +P _(PUSCH(Retransmission)) >P _(Max)  Case1-10:

Case 1-10 corresponds to the case where the sum of transmission powersof PUSCHs transmitting retransmission data reaches a maximum powerlimitation. The following options may be considered.

Option 1: The priority determination method described in Case 1-1 may beused without considering retransmission. For example, PUSCHs may begiven the same priority. In this case, powers of the PUSCHs may bereduced at the same rate. Different priority may be allocated to thePUSCHs in consideration of transport formats of the PUSCHs.

Option 2: Since retransmission may occur due to reduction of atransmission power during previous transmission, high priority may beallocated to a PUSCH having a greater number of retransmissions toimprove a reception rate of a retransmitted PUSCH.

P _(PUSCH(Retransmission)) +P _(PUCCH) /P _(SRS) >P _(Max)  Case 1-11:

Case 1-11 corresponds to the case where the sum of transmission powersof a PUSCH transmitting retransmission data and a PUCCH/SRS reaches amaximum power limitation. The following operations may be considered.

Option 1: The priority determination methods described in Case 1-2 andCase 1-3 may be used without considering retransmission.

Option 2: Since retransmission may occur due to reduction of atransmission power during previous transmission, high priority may beallocated to a retransmitted PUSCH to improve a reception rate of thePUSCH.

Embodiment 2: Power Control Per CC (Group)

The transmission power control methods of the UE described up to now areuseful when the UE has one power amplifier. However, in an LTE-A system,a plurality of CCs may be allocated to the UE and the allocated CCs maybe successive or separate bands in a frequency domain. If the allocatedCCs exist as separate bands, since it is difficult for the UE to amplifya power in a wide frequency domain using only one power amplifier, aplurality of power amplifiers may be needed. In this case, each poweramplifier may be in charge of power amplification of only one CC or onlya CC group comprised of some CCs. Accordingly, even if the UE has aplurality of power amplifiers, power control may be naturally applied byextending the above proposed methods to power control methods per CC orCC group.

Hereinafter, operation of a UE according to an exemplary embodiment ofthe present invention will be described, when the UE reaches atransmission power limitation of a specific CC (group), the UE reaches atotal transmission power limitation, or the UE reaches the above twopower limitations, in an environment where both the transmission powerlimitation per CC (group) and the total transmission power limitation ofthe UE are present.

Generally, a UL transmission power of a UE may be limited as indicatedby the following Equation 1:

$\begin{matrix}{P^{UE} \leq {\min\left( {P_{Max}^{UE},{\sum\limits_{CC}\; {\min\left( {P_{\max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

If a quantization level of a power amplifier of the UE is sufficientlyhigh, an equality may be satisfied as indicated by Equation 2:

$\begin{matrix}{P^{UE} = {\min\left( {P_{\max}^{UE},{\sum\limits_{CC}\; {\min\left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Symbols used in the above equation are defined as follows.

P^(UE): UL transmission power of a UE

P_(Max) ^(UE) (P_(Max)): A maximum transmission power (or transmissionpower limitation value) of a UE. In other words, this indicates amaximum transmission power (or transmission power limitation value) withrespect to all CCs. The maximum transmission power value of the UE maybe determined by a total transmittable power of the UE or may bedetermined by combination with a value set in a network (e.g. a BS).Information about the maximum transmission power value of the UE may beindicated through upper layer signaling. For example, the informationabout the maximum transmission power value of the UE may becell-specifically signaled through a broadcast message or may beUE-specifically or UE group-specifically signaled through an RRCmessage.

P_(Max) ^(CC=i): A maximum transmission power (or transmission powerlimitation value) in an i-th CC (group). The maximum transmission powervalue per CC (group) may be determined by a total transmittable power ofthe UE or a transmittable power per CC (group) or may be determined bycombination with a value set per CC (group) in a network (e.g. a BS).Information about the maximum transmission power value per CC (group)may be indicated through upper layer signaling. For example, theinformation about the maximum transmission power value per CC (group)may be cell-specifically signaled through a broadcast message or may beUE-specifically or UE group-specifically signaled through an RRCmessage. Meanwhile, the maximum transmission power value per CC (group)may be signaled in consideration of information about interference (orcoverage) with another UE (or CC (group)). Information about the maximumtransmission power value per CC (group) may include information aboutinterference (or coverage) with another UE (or CC (group)). The maximumtransmission power per CC (group) may have the same value in all CCs (CCgroups).

P_(Ch=j) ^(CC=i): A transmission power of a j-th channel of an i-th CC(group).

Case 2-1:

${\sum\limits_{CC}\; {\min\left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}} \leq P_{Max}^{UE}$

Case 2-1 is when the sum of maximum transmission powers of CCs (CCgroups) in all CCs (CC groups) is less than a maximum transmission powerof a UE and simultaneously the sum of maximum transmission powers ofchannels of all CCs (CC groups) is less than the maximum transmissionpower of the UE. Since a transmission power of the UE is not limited toa total transmission power value, a simplified Equation 3 may besatisfied:

$\begin{matrix}{{P^{UE} \leq {\sum\limits_{CC}\; {\min\left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}}} = {{\sum\limits_{{CC} \in S}\; P_{Max}^{{CC} = i}} + {\sum\limits_{{CC} \in s^{c}}\; {\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

If a quantization level of a power amplifier of the UE is sufficientlyhigh, an equality may be satisfied as indicated by Equation 4:

$\begin{matrix}{P^{UE} = {{\sum\limits_{CC}\; {\min\left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}} = {{\sum\limits_{{CC} \in S}\; P_{Max}^{{CC} = i}} + {\sum\limits_{{CC} \in s^{c}}\; {\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Equation 3 and Equation 4, a set S refers to a set of a CC (group) inwhich the sum of transmission powers of channels within a CC (group)exceeds a maximum transmission power value of a CC (group)

$\left( {{i.e.\mspace{14mu} P_{Max}^{{CC} = i}} \leq {\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right).$

In this case, the sum of the transmission powers is controlled not toexceed the maximum transmission power of the CC (group) only within theset S. Power control may be performed by introducing an attenuationcoefficient. For example, power control may be simplified as a methodfor searching for an attenuation coefficient α_(j) ^(i) (0≦α_(j) ^(i)≦1)for a transmission power of each channel as indicated by Equation 5:

$\begin{matrix}{{{\sum\limits_{Ch}\; {\alpha_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}} \leq P_{Max}^{{CC} = i}},{{{where}\mspace{14mu} i} \in S}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Case 2-2

${\sum\limits_{CC}\; {\min\left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}} > P_{Max}^{UE}$

Case 2-2 corresponds to the case where a maximum transmission power of aUE is less than the sum of maximum transmission powers of a CC (group)and simultaneously less than the sum of transmission powers of allchannels. Since a transmission power of the UE is limited by the maximumtransmission power value, Equation 6 is satisfied:

P ^(UE) ≦P _(Max) ^(UE)  [Equation 6]

If a quantization level of a power amplifier of the UE is sufficientlyhigh, an equality may be satisfied as indicated by Equation 7:

P ^(UE) =P _(Max) ^(UE)  [Equation 7]

In this case, the transmission power of the UE can be reduced to themaximum transmission power of the UE as in Case 2-1. The sum oftransmission powers of channels within each CC (group) should be lessthan a maximum transmission power of the CC (group) and the sum oftransmission powers of all CCs (CC groups) should be less than themaximum transmission power value of the UE. Power control may besimplified as a method for searching for an attenuation coefficientα_(j) ^(i) (0≦α_(j) ^(i)≦1) for a transmission power of each channel asindicated by Equation 8:

$\begin{matrix}{{{{\sum\limits_{Ch}\; {\alpha_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}} \leq P_{Max}^{{CC} = i}},{{{where}\mspace{14mu} i} \in S}}{{\sum\limits_{CC}\; {\sum\limits_{Ch}\; {\alpha_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}} \leq P_{Max}^{UE}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Since the methods described in Cases 2-1 and 2-2 calculate anattenuation coefficient through optimization for the two cases oflimitation (total transmission power limitation and CC (group)transmission power limitation), problems of performing optimizationusing a somewhat complex method may occur. Accordingly, methods forefficiently calculating the attenuation efficient are described withreference to FIGS. 10 and 11.

In FIGS. 10 and 11, the horizontal axis denotes a CC (group) and thevertical axis denotes power strength. A hatching box in each CC (group)indicates a channel within a corresponding CC (group). Hatching is shownfor convenience to denote a channel. Respective hatchings may meandifferent channels or the same channel. In FIGS. 10 and 11, it isassumed that the sum of transmission powers of CCs (CC groups) isgreater than a maximum transmission power value P_UE_MAX of a UE and thesums of transmission powers of channels within CCs (CC groups) 1 and 3exceed maximum transmission powers P_CC1_MAX and P_CC3_MAX of the CCs(CC groups), respectively (view (a) of FIG. 10 and view (a) of FIG. 11).The CCs (CC groups) 1 and 3 constitute the set S described withreference to Equation 3 and Equation 4.

FIG. 10, including views (a), (b) and (c), illustrates a method forcalculating an attenuation coefficient for power control according to anembodiment of the present invention. Referring to FIG. 10, anattenuation coefficient for power control is calculated in two steps. Inthe first step, transmission powers of channels in a set S may beattenuated to satisfy a transmission power limitation criterion of a CC(group). In the first step, an attenuation coefficient α_(j) ^(i) may beindependently determined according to Equation 9:

$\begin{matrix}{{{\alpha_{j}^{i}\mspace{14mu} {s.t.\mspace{14mu} {\sum\limits_{Ch}\; {\alpha_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}} \leq P_{Max}^{{CC} = i}},{{{where}\mspace{14mu} i} \in S}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

It can be seen from view (b) of FIG. 10 that the sums of transmissionpowers of channels within CCs (CC groups) 1 and 3 are reduced to maximumtransmission power values of the corresponding CCs (CC groups),respectively.

However, in view (b) of FIG. 10, the sum of transmission powers of CCs(CC groups) is still greater than the maximum transmission power valueP_UE_MAX of the UE. Thus, if a total transmission power limitation ofthe UE is not satisfied even though the transmission powers of channelswithin the set S are reduced, transmission powers of all channels of allCCs (CC groups) are reduced to satisfy the total transmission powerlimitation in the second step. In the second step, an attenuationcoefficient β_(j) ^(i) may be independently determined according toEquation 10:

$\begin{matrix}{{{\beta_{j}^{i}\mspace{14mu} {s.t.\mspace{14mu} {\sum\limits_{{CC} \in S}\; {\sum\limits_{Ch}\; {\beta_{j}^{i} \times \alpha_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}}} + {\sum\limits_{{CC} \in s^{c}}\; {\sum\limits_{Ch}\; {\beta_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}} \leq P_{Max}^{UE}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

It can be seen from view (c) of FIG. 10 that the sum of transmissionpowers of all channels is reduced to the total transmission powerlimitation value P_UE_MAX of the UE. For brevity, the attenuationcoefficient β_(j) ^(i) of a channel in the set S may be set to 1 andβ_(j) ^(i) may be determined only with respect to a complementary set ofthe set S. Alternatively, the attenuation coefficient β_(j) ^(i) of achannel in the complementary set of the set S may be set to 1 and β_(j)^(i) may be determined only with respect to the set S.

FIG. 11, including views (a), (b), (c) and (d), illustrates a method forcalculating an attenuation coefficient for power control according toanother embodiment of the present invention. Referring to FIG. 11, anattenuation coefficient for power control is basically calculated in twosteps and an addition step may be further included for powercompensation. In the first step, transmission powers of channels in allCCs (CC groups) may be attenuated to satisfy a total transmission powerlimitation criterion of a UE. An attenuation coefficient β_(j) ^(i) maybe independently determined according to Equation 11:

$\begin{matrix}{{\beta_{j}^{i}\mspace{14mu} {s.t.\mspace{14mu} {\sum\limits_{CC}\; {\sum\limits_{Ch}\; {\beta_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}}} \leq P_{Max}^{UE}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

It can be seen from view (b) of FIG. 11 that transmission powers ofchannels in all CCs (CC groups) are reduced so that the sum oftransmission powers of all channels coincides with a total transmissionpower limitation value P_UE_MAX of a UE.

However, in view (b) of FIG. 11, the sum of transmission powers ofchannels of a CC (group) 3 is still greater than a power limitationvalue P_CC3_MAX of the CC (group) 3. Thus, if there is a CC (group)(i.e. a set S) which does not satisfy a transmission power limitation ofa CC (group) even though the transmission powers of channels in all CCs(CC groups) are reduced, transmission powers of channels of all CCs (CCgroups) within the set S may be reduced in the second step. Anattenuation coefficient α_(j) ^(i) may be independently determinedaccording to a condition of Equation 12:

$\begin{matrix}{{{\alpha_{j}^{i}\mspace{14mu} {s.t.{\sum\limits_{Ch}\; {\alpha_{j}^{i} \times \beta_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}} \leq P_{Max}^{{CC} = i}},{{{where}\mspace{14mu} i} \in S}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

It can be seen from view (c) of FIG. 11 that the sum of transmissionpowers of channels of the CC (group) 3 (i.e. set S) is reduced to themaximum transmission power value P_CC3_MAX of the corresponding CC(group).

Next, in the third step, a power amount

$P_{R - {SUM}} = {\sum\limits_{{CC} \in S}\; {\sum\limits_{Ch}\; {\left( {1 - \alpha_{j}^{i}} \right) \times \beta_{j}^{i} \times P_{{Ch} = j}^{{CC} = i}}}}$

reduced from channels of the set S may be compensated for channels in acomplementary set of the set S. A power after compensation of channelsshould not exceed a maximum transmission power value of a correspondingCC (group). Referring to view (d) of FIG. 11, a power reduced from theCC (group) 3 in the second step is compensated for a CC (group) 2. Asopposed to (d) of FIG. 11, the power reduced from the CC (group) 3 inthe second step may be compensated for a CC (group) 1. The following isconsidered as a power compensation method.

{circle around (1)} Priority criterion: Priority is allocated accordingto a degree of urgency or importance of a message in channels (PUCCH,PUSCH, and SRS) and a more power is allocated to a channel having higherpriority.

{circle around (2)} Same compensation amount: Powers of the same amountare compensated for all channels of a complementary set of a set S.

{circle around (3)} Same compensation rate: Powers are compensated forall channels of the complementary set of the set S at the same rate.

{circle around (4)} Powers are compensated using possible combinationsof {circle around (1)}, {circle around (2)} and {circle around (3)}

The attenuation coefficients α_(j) ^(i), and β_(j) ^(i) described withreference to FIGS. 10 and 11 may be determined in various ways. Acriterion for determining the attenuation coefficients α_(j) ^(i), andβ_(j) ^(i) may consider, but without being limited to, priority, thesame attenuation amount, the same attenuation rate, or combinationsthereof.

In the priority criterion method, priority is allocated to respectivechannels according to a degree of urgency or importance of a message inchannels (e.g. PUCCH, PUSCH, and SRS) and a greater attenuationcoefficient value is allocated to a channel having higher priority. Thatis, this method ensures that a reception rate is increased for a channelhaving high priority and a statistically low reception rate is providedto a channel having low priority. Accordingly, a power is reducedbeginning from a channel having low priority. Priority of channels maybe determined according to the above-described Cases 1-1 to 1-11 andpriority between CCs may be additionally considered. For example, if aUE attempts UL transmission using multiple CCs, important controlinformation or an important message among UL transmission messages maybe transmitted to a specific CC first. In this case, high priority maybe allocated to the specific CC to which the important controlinformation is transmitted.

The priority criterion method may be modified to a simpler method byrestricting the attenuation coefficient to 0 or 1 (α_(j) ^(i),β_(j)^(i)ε{0,1}). Namely, a transmission power of 0 may be sequentiallyallocated beginning from a channel having low priority within a CC(group) so that the sum of transmission powers of channels is less thana transmission power limitation value P_(Max) ^(CC=i) of a CC (group).Consequently, a channel having low priority is not transmitted and achannel having high priority is transmitted at an original transmissionpower.

The same attenuation amount criterion method serves to reduce the sameamount of powers of all channels within each CC (group) which exceeds atransmission power limitation of a CC (group). That is, all channelswithin a CC (group) are subject to the same power attenuation penalty.This method may be useful when a difference between the sum oftransmission powers of channels within a CC (group) and a maximumtransmission power value of the CC (group) is insignificant. The sameattenuation rate criterion method may apply the same attenuationcoefficient to all channels within each CC (group) which exceeds atransmission power limitation of the CC (group). The same attenuationamount criterion method corresponds to a method for reducing the sameamount of power in a linear scale, whereas the same attenuation ratecriterion method corresponds to a method for reducing the same amount ofpower in a dB scale.

Embodiment 3: Power Control Per Antenna in MIMO

The above-described power control methods may be applied in the sameways even in transmission through transmit (Tx) diversity or spatialmultiplexing using MIMO. In this case, the above-described methodscorrespond to operation in layers, streams, or antennas. If a UEincludes a plurality of transmission antennas, a maximum transmissionpower in a power amplifier of each antenna may be limited to P_(Max)^(antenna,n) (where n is an antenna index). A maximum transmission powerof each antenna may be limited by a characteristic (e.g. class) of apower amplifier or may be (additionally) limited through broadcast orRRC signaling. An upper limit of a transmission power which can be usedby the UE is limited by a minimum value of the sum of maximumtransmission powers of antennas and a maximum transmission power of a UEas indicated by Equation 13:

$\begin{matrix}{P^{UE} = {\min\left( {P_{Max}^{UE},{\sum\limits_{n}\; P_{Max}^{{antenna},n}}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

If a transmission power per CC (group) is limited, the upper limit of atransmission power which can be used by the UE may be expressed byEquation 14:

$\begin{matrix}{P^{UE} = {\sum\limits_{n}\; {\min \begin{pmatrix}{P_{Max}^{{antenna},n},} \\{\sum\limits_{{CC}\mspace{14mu} {in}\mspace{14mu} {Antenna}\mspace{14mu} n}\; {\min \left( {P_{Max}^{{CC} = i},{\sum\limits_{Ch}\; P_{{Ch} = j}^{{CC} = i}}} \right)}}\end{pmatrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Hereinafter, operation of a UE is proposed when power control isindependently performed with respect to each antenna. For convenience,only two antennas are described by way of example but it is possible toapply the present invention to three or more antennas. The followingsymbols are defined.

P_(X-CH) ^(antenna,n): A power calculated to be allocated to an n-thantenna. An actually allocated power may be less than this power by apower limitation. When there is no dB sign, this means a linear scale.X-CH denotes all physical channels (e.g. PUSCH, PUCCH, SRS, orcombinations thereof) transmitted to an antenna n.

If P_(X-CH) ^(antenna,n)>P_(Max) ^(antenna,n), P_(X-CH)^(antenna,m)≦P_(Max) ^(antenna,m), one antenna reaches a maximum powerlimitation and the other antenna does not reach the maximum powerlimitation. In this case, power control may be performed per antenna asfollows.

Step 1: A transmission power for each CC (group) may be controlled as inEmbodiment 2 according to a maximum transmission power limitationP_(Max) ^(CC=i) per CC (group). Namely, if the sum of the transmissionpowers of channels of all antennas per CC (group) exceeds P_(Max)^(CC=i), a transmission power is controlled. Step 1 is included only inthe case where power control per CC (group) is performed.

Step 2: A transmission power of each antenna may be controlled as in thefollowing options in consideration of a maximum transmission power of anantenna. The transmission power of an antenna may be controlled byapplying the various methods (e.g. priority) described in Embodiment 1and Embodiment 2.

Option 1: When a plurality of transmission antennas is used, precodingmay be performed for transmission. In order for a receiving end todecode a precoded signal, the receiving end should perform decoding inreverse order of the transmitting end by recognizing a precoding matrixused in the transmitting end. However, if a power ratio of antennas isnot maintained by power limitation of an antenna, distortion may occurin the precoding matrix applied from the transmitting end, therebyincreasing an error rate. Accordingly, distortion of the precodingmatrix can be prevented by adjusting a power of an antenna without atransmission power limitation at the same rate according to an antennawith a transmission power limitation. That is, a transmission power ofan antenna which does not reach a maximum power limitation is reducedtogether with a transmission power of an antenna which exceeds a powerlimitation so that a transmission power ratio is maintained at the samelevel. If three or more antennas are present, according to atransmission power of an antenna reduced in the largest ratio,transmission powers of the other antennas may be adjusted at the samerate. In Option 1, an actually transmitted power {circumflex over (P)}is as follows:

{circumflex over (P)} _(X-CH) ^(antenna,n) =P _(X-CH) ^(antenna,n) ,{circumflex over (P)} _(X-CH) ^(antenna,m) =P _(X-CH)^(antenna,m)  [Equation 15]

Equation 15 indicates an actual transmission power when there is nopower limitation.

{circumflex over (P)} _(X-CH) ^(antenna,n) =P _(Max) ^(antenna,n) ,{circumflex over (P)} _(X-CH) ^(antenna,m)=(P _(Max) ^(antenna,n) /P_(X-CH) ^(antenna,n))P _(X-CH) ^(antenna,m)  [Equation 16]

Equation 16 indicates an actual transmission power when there is a powerlimitation. Referring to Equation 16, since the sum of transmissionpowers of channels in an antenna n exceeds a maximum transmission power,an actual transmission power of the antenna n is limited to the maximumtransmission power. Meanwhile, even if the sum of transmission powers ofchannels of an antenna m does not exceed a maximum transmission power, atransmission power of the antenna m is reduced in the ratio of P_(Max)^(antenna,n)/P_(X-CH) ^(antenna,n) so that the ratio of a transmissionpower to the antenna n is maintained.

Option 2: if a power ratio of each antenna indicated by a power controlsignal is not maintained due to a power limitation of any one antenna,distortion occurs in a precoding matrix applied from a transmitting end.If a receiving end does not recognize degree of distortion, a receptionerror rate is increased. However, when indirectly estimating theprecoding matrix used in the transmitting end through a DedicatedReference Signal (DRS), the receiving end may also estimate distortionof the precoding matrix according to variation of a transmission powerratio of an antenna. In this case, a transmission power of an antennawithout a power limitation may not be lowered in order to control atransmission power ratio as in Option 1. Accordingly, only atransmission power of an antenna reaching a maximum power limitation maybe transmitted by clipping a maximum transmission power of acorresponding antenna. A power used in actual transmission in Option 2is as follows:

{circumflex over (P)} _(X-CH) ^(antenna,n) =P _(X-CH) ^(antenna,n) ,{circumflex over (P)} _(X-CH) ^(antenna,m) =P _(X-CH)^(antenna,m)  [Equation 17]

Equation 17 indicates an actual transmission power when there is nopower limitation.

{circumflex over (P)} _(X-CH) ^(antenna,n) =P _(Max) ^(antenna,n) ,{circumflex over (P)} _(X-CH) ^(antenna,m) =P _(X-CH)^(antenna,m)  [Equation 18]

Equation 18 indicates an actual transmission power when there is a powerlimitation. Referring to Equation 18, since the sum of transmissionpowers of channels in an antenna n exceeds a maximum transmission power,an actual transmission power of the antenna n is limited to a maximumtransmission power. Meanwhile since the sum of transmission powers ofchannels in an antenna m does not exceed the maximum transmission power,transmission is performed without power control.

FIG. 12 illustrates a BS and a UE that are applicable to the embodimentsof the present invention.

Referring to FIG. 12, a wireless communication system includes a BS 110and a UE 120. In DL, a transmitter is a part of the BS 110 and areceiver is a part of the UE 120. In UL, the transmitter is a part ofthe UE 120 and the receiver is a part of the BS 110. The BS 110 includesa processor 112, a memory 114, and an RF unit 116. The processor 112 maybe configured to implement the procedures and/or methods proposed in thepresent invention. The memory 114 is connected to the processor 112 andstores various information related to the operation of the processor112. The RF unit 116 is connected to the processor 112 and transmits andreceives radio signals. The UE 120 includes a processor 122, a memory124, and an RF unit 126. The processor 122 may be configured toimplement the procedures and/or methods proposed in the presentinvention. The memory 124 is connected to the processor 122 and storesvarious information related to the operation of the processor 122. TheRF unit 126 is connected to the processor 122 and transmits and receivesradio signals. The BS 110 and/or the UE 120 may include a single antennaor multiple antennas.

The above-described exemplary embodiments are combinations of elementsand features of the present invention. The elements or features may beconsidered selective unless otherwise mentioned. Each element or featuremay be practiced without being combined with other elements or features.Further, the embodiments of the present invention may be constructed bycombining parts of the elements and/or features. Operation ordersdescribed in the embodiments of the present invention may be rearranged.Some constructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment. It is apparent that the embodiments may beconstructed by a combination of claims which do not have an explicitcited relation in the appended claims or may include new claims byamendment after application.

In the present document, a description has been made of a datatransmission and reception relationship between a UE and a BS. Here, aspecific operation described as performed by the BS may be performed byan upper node of the BS. Namely, it is apparent that, in a networkcomprised of a plurality of network nodes including the BS, variousoperations performed for communication with the UE may be performed bythe BS, or network nodes other than the BS. The term Bs may be replacedwith the term fixed station, Node B, eNode B (eNB), access point, etc.The term UE may be replaced with the term Mobile Station (MS), MobileSubscriber Station (MSS), etc.

The exemplary embodiments of the present invention may be achieved byvarious means, for example, hardware, firmware, software, or acombination thereof. In a hardware configuration, the exemplaryembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the exemplary embodiments ofthe present invention may be achieved by a module, a procedure, afunction, etc. performing the above-described functions or operations.Software code may be stored in a memory unit and executed by aprocessor. The memory unit may be located at the interior or exterior ofthe processor and may transmit and receive data to and from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The present invention may be applied to a wireless communication system.Specifically, the present invention may be applied to a method andapparatus for controlling a UL transmission power.

What is claimed is:
 1. A method for controlling transmission powers by acommunication apparatus in a wireless communication system supporting aplurality of component carriers, the method comprising: when a soundingreference symbol (SRS) transmission overlaps with a physical uplinkshared channel (PUSCH) transmission in a time domain, checking whether atotal of a PUSCH transmission power for the PUSCH transmission on afirst component carrier and a SRS transmission power for the SRStransmission on a second component carrier exceeds a maximumtransmission power configured for the communication apparatus; anddropping the SRS transmission if the total of the PUSCH transmissionpower and the SRS transmission power exceeds the maximum transmissionpower configured for the communication apparatus.
 2. The method of claim1, further comprising: transmitting the PUSCH on the first componentcarrier.
 3. The method of claim 1, further comprising: calculating thePUSCH transmission power for the PUSCH transmission; and calculating theSRS transmission power for the SRS transmission.
 4. A communicationapparatus for controlling transmission powers in a wirelesscommunication system supporting a plurality of component carriers, thecommunication apparatus comprising: a processor configured to: when asounding reference symbol (SRS) transmission overlaps with a physicaluplink shared channel (PUSCH) transmission in a time domain, checkwhether a total of a PUSCH transmission power for the PUSCH transmissionon a first component carrier and a SRS transmission power for the SRStransmission on a second component carrier exceeds a maximumtransmission power configured for the communication apparatus; and dropthe SRS transmission if the total of the PUSCH transmission power andthe SRS transmission power exceeds the maximum transmission powerconfigured for the communication apparatus.
 5. The communicationapparatus of claim 4, further comprising: a transmitter configured totransmit the PUSCH on the first component carrier.
 6. The communicationapparatus of claim 4, wherein the processor is further configured to:calculate the PUSCH transmission power for the PUSCH transmission; andcalculate the SRS transmission power for the SRS transmission.